Sirius XM Posts Screenshot Of iPhone App

Today is Sirius XM's shareholder summit, and the SEC just published Mel Karmazin's PowerPoint presentation. One of the slides includes a screenshot of its forthcoming iPhone app, which the company hopes will be a growth driver/subscriber retainer.

It looks like you'll be able to browse music by categories, channels, and favorites. And there is a "shopping" feature, which might tie into Apple's iTunes store.

From what we understand, the app download will be free. But you'll need to be considered a Sirius "streaming" subscriber to use the service, either through a $3/month add-on to your in-car subscription, or a standalone, $13/month streaming subscription (if you don't get Sirius on an actual radio).

What's on it? On Sirius XM's last earnings call, the company talked up some of the content that'll be on the app:

"The SIRIUS XM app will deliver an expanded programming lineup that includes SIRIUS XM's exclusive sports talk, news, comedy, and 100% commercial free music channel, as well as new talk, comedy, and music showcase channels."

While it definitely makes sense for the satellite radio company to open up its content to new platforms like Apple's (AAPL) portable gadgets -- this seems like a good deal for existing Sirius subscribers -- it's hard to see iPhone users signing up as new subs in droves.

Why not? There are plenty of free, ad-supported music and streaming radio services on the iPhone already; other apps like MLB's At Bat -- which includes live radio streams of all baseball games -- replace some of Sirius XM's "exclusive" content; and it seems that any diehard Howard Stern fan would already have a Sirius subscription. (That said, free apps include ads, so it's possible some would pay extra to hear commercial-free music.)

So, probably not going to drive a whole lot of new subscriber growth. But can't hurt, especially if it helps keep some subscribers from churning off Sirius -- and paying an extra $3/month in service fees.